This paper presents a sensorless control strategy for pulsewidth modulated active filters. The complete solution uses only two current sensors, which are located in the grid interface. The ...compensation is performed by the imposition of sinusoidal current references in the grid, and does not require algorithms for disturbance estimation. The virtual flux concept for grid synchronization and multiple quasi-resonant compensators in the current scheme are employed for selective harmonic mitigation. A discretization analysis is presented in order to obtain a precise digital realization of the current controllers. It is proposed as a regulator for the direct-current bus voltage in the active filter, which employs only information of the modulated voltage and is compatible with the previous sensorless synchronization solution. Experimental results from a 1-kVA prototype converter are presented, covering the solution with and without the voltage sensor in the direct current bus. Analyses of stationary and transient responses are performed by using a six-pulse diode rectifier as nonlinear load.
This paper presents an universal active power filter for harmonic and reactive power compensation with uninterrupted power supplies (UPS) features. The configurations does not use transformer in the ...series part. Transformerless modern UPS systems have been rapidly replacing the old technology due to their performance and size attributes. Reducing the numbers of passive elements and/or switches in active power filters and UPS topologies not only reduces the cost of the whole system but also provides some advantages, such as great compactness, smaller weight, and higher reliability. However, the cost reduction requires the use of more complex control strategies. The model of the proposed system is derived and it is observed that the system can be reconfigurable to operate with four or three leg depending on the issue. A complete control system, including the pulsewidth modulation techniques, is developed and a comparison between the proposed filter and the standard one is done, as well. Simulated and experimental results validate the theoretical considerations.
This paper presents a control technique based on input and output AC power synchronization to reduce the low frequency AC power and the DC-link voltage fluctuation of a single-phase full-bridge ...converter. The control technique is based on a technique in which the load voltage is synchronized with the input grid voltage for both constant (Mode I) and variable (Mode II) phase angle. Such approach allows for a reduction in the capacitor size. A capacitor bank design approach is also proposed. The technique has been achieved for the same input and output converter frequency. Simulated and experimental results are addressed.
The digital scalar pulse-width modulation (DSPWM) gathers the characteristics of simplicity of implementation found in the regular sampling with the flexibility of manipulation of the switching ...patterns in the space vector modulation (SVPWM). This paper establishes a correlation between the SVPWM and DSPWM techniques.
Transmission constraints and market concentration may prevent power markets from being fully competitive, allowing firms to exercise market power and raise prices above marginal cost. We present a ...strategic gaming model for analyzing such markets; it represents an oligopolistic market economy consisting of several dominant firms in an electric power network. Each generating firm submits bids to an ISO, choosing its bids to maximize profits subject to anticipated reactions by rival firms. The single-firm model is formulated as a mathematical program with equilibrium constraints (MPEC) with a parameter-dependent spatial price equilibrium problem as the inner problem. Power flows and pricing strategies are constrained by the ISO's linearized DC optimal power flow (OFF) model. A penalty interior point algorithm is used to compute a local optimal solution of the MPEC. Numerical examples based on a 30 bus network are presented, including multi-firm Nash equilibria in which each player solves an MPEC of the single-firm type.
This paper analyzes the use of pulsating high-frequency signal injection for islanding detection purposes. Active islanding detection using high-frequency signal injection is an appealing option due ...to its reduced nondetection zone, reduced cost, and ease of implementation. The use of a rotating high-frequency signal has been reported and analyzed. However, this method can only be applied to three-phase systems. In this paper, the use of a pulsating high-frequency signal injection is proposed. While it uses the same principles as rotating signal injection, it can be applied to both three-phase and single-phase systems.
This paper proposes a single-stage electronic ballast for high-intensity discharge lamps. The ballast consists of the integration of a boost converter in discontinuous conduction mode (DCM) and a ...full-bridge LCC resonant inverter. The boost semi-stage working in DCM functions as a power factor corrector and the inverter semi-stage operated above resonance is employed to drive the lamp. The sine-wave approximation is used to design the inverter at steady-state. The proposed electronic ballast can save a controller, reduce size and possibly increase system reliability compared to conventional two-stage system. The proposed ballast is analyzed, simulated and experimentally verified with a 125 W HPS lamp.
The authors discuss the original paper ("On the measurement of overhead transmission lines conductor self-damping", G. Diana et al., see ibid., vol.15, no.1, p.285-92, 2000) and present their ...observations. The original authors; response is also included.
This paper examines two new bidirectional hybrid dc circuit breaker (CB) topologies for application in meshed dc grids. The goal is to retain performance of hybrid dc CB with bidirectional current ...interruption while reducing semiconductor count, dc CB size, and weight. The fault current is routed to the unidirectional internal valve using multiple additional ultrafast disconnectors. Operation of both topologies is studied using a 320-kV, 16-kA simulation model, as well as demonstrated on a 900-V, 500-A lab prototype. The control systems are presented and discussed in detail. The low-voltage hardware prototypes verify performance of several new technical and operating solutions in laboratory conditions. A comparison is made with the existing dc CB topologies and performance and reliability compromises of each topology are assessed. The conclusion is that it might be possible to halve the dc CB semiconductor count while retaining same 2 ms opening speed and bidirectional operation.
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